How to know when the layout has changed?

Hi Gregory,
That is very helpful thanx. A quick read about the TdxLayoutContainer control in the help made for fairly sparse reading. Is there one of these for each TdxLayoutControl? Or one for each TdxLayoutItem, or one for each TdxLayoutGroup? Seems this component is the corner stone of the layout engine, so need to learn a lot more about it.
regards,
-randall

Hello Randall,

There are no such events in LayoutControl Items and Groups.

Hi Mikhail,
Well, that's not true.These two lines compile fine:
 dxlayoutControl.Container.OnChanged := LayoutChanged;
 liGridPhone.Container.OnChanged := LayoutChanged;
But that is no surprising now that I've looked closer at the source… Layout Items, Groups and Controls all derive from TdxCustomLayoutItem which surfaces the Container property hence the reason I asked. But it would appear both point to the same TdxLayoutContainer object.
In addition, Gregories original advise is not good… The Container's OnChange is already assigned to something internally:
procedure TdxCustomLayoutControl.CreateContainer;
begin
 [snip]
 FContainer.OnChanged := ContainerChangedHandler;
 [snip]
end;
So if you REALLY want to assign your own, you will need to do what ContainerChangedHandler does. Something like this:
type THackLayoutControl = class(TdxLayoutControl);
procedure TForm7.LayoutChanged(Sender: TObject);
var hackedLayoutControl : THackLayoutControl;
begin
 [do what I want special here]
 hackedLayoutControl := THackLayoutControl((sender as TdxLayoutControlContainer).Control);
 hackedLayoutControl.CheckPositions;
 hackedLayoutControl.Invalidate;
 hackedLayoutControl.PostBuildSelectionLayer;
end;
The bottom line is that the layout controls lack the level of granularity I'm looking for to truly take control over them. All changes funnel into a single OnChanged event handler. What would be much nicer would be an OnLayoutChanging/ed event that passed in various params to signify what will be changing and what has changed, eg alignment, direction, captions, etc.
So I guess have to ask… have I missed something somewhere, where I can take control of the Express Layout library at this level? From what I can see, I'm going to need to do a LOT of subclassing so I can trigger off the aformentioned event handler that I write myself.
regards,
-randall

Hello Randall,

<<So if you REALLY want to assign your own, you will need to do what ContainerChangedHandler does. Something like this:>>
No, your conclusion is incorrect. Gregory just showed where you need to store the previous event handler and restore it after your actions.

As for the control over all changed items, I'm afraid there is no such event where you could see what will be changed and what was changed.
However, I can create a corresponding suggestion if you describe in what view you wish to see this event. Let me explain. When you change the Item position, other Items change their position and they could also change their parents and alignment, auto-created groups could be created, so on.

Hi Mikhail,
Yes you are right, one could also daisy-chain the handler but that is neither here nor there as it is not a potential solution. It is called far to frequently. For example, if you scroll down a page it calls the container's OnChange.
What I am really looking for (my wish list) is an OnLayoutChanging and OnLayoutChanged events. That would correspond to anything that changes (or potentially changes) the visual layout, So that would include things like sizing, borders, captions, alignments, alignment directions etc.
The reason I'm looking for such functionality is to facilitate the user's customization of their layout. In short, the current customization form is too complex for your average user. These guys struggle to get their iPhones to behave. So although the customization form is great for power users, our users need it to be dummed down. And the easiest way for me to do that is to remove functionality from the Customization form and/or subclass it in conjunction with taking actions on their behalf. For example, if we are doing a vertical layout, and groups have their captions on top, if they want to instead lay things out horizontally, they would need to manually change the caption for each internal group from top to left. So instead I would do this automatically.
Ideally, a well implemented OnLayoutChanged/ing event would pass the layout item or group that was changed, and some sort of type constant denoting what was changed, eg lcCaption, lcBorder, lcLayoutDirection, lcAlignHorz, lcAlignVert etc.
As for item/group creation and destruction, they would probably need their own event handlers so the developer can access the newly created (or about to be deleted) item or group.
regards,
-randall sell

Thank you Randall.

We will discuss your comment with our developers, but it can take us some time.

Randall,

I've created a separate thread about implementing the OnLayoutChanged event - T167891: Implement a new OnLayoutChanged/ing for TdxLayoutControl.
<<And the easiest way for me to do that is to remove functionality from the Customization form and/or subclass it in conjunction with taking actions on their behalf.>>
Perhaps using the QuickCustomize or/and TdxLayoutGroup.AllowFloating can help you. Please take a look at the "TdxCustomLayoutItem.AllowQuickCustomize" help topic for information.

Um, 12.1.9 does not have either of these methods/properties. Was that a mis-type on your part, or something incorporated in a newer DX version? I was going to move up to 13.2.7 when I had the time.
regards,
-randall

No, this functionality is only supported in the latest versions of our controls (VCL 14.1). I'm afraid it will not be implemented in our outdated versions.